When they do tracking poll plots like they they should really make the thickness of the bars equal to the MOE so you can tell when a difference is p<0.05. Otherwise you might as well disconnect the cable from your TV and pretend you can make out an I Love Lucy rerun in the static.

Has Gallup started adjusting for likely voters yet? I don't believe so. Remember, according to their own website, those numbers aren't worth squat until they do. And Rasmussen, which IS so adjusting, puts the numbers at 48% to 36% in favor of the Republicans.

Further, Gallup themselves in this poll say that levels of Republican enthusiasm are at historic highs, (While Democrats are going into the election bummed out.) which suggests that turnout might be even more tilted Republican than usual.

I suppose it's a straw, so you CAN grasp at it if you like. But I wouldn't bet any real money based on this.

The straw to grasp at is perhaps that the fluctuations suggest a genuine volatility or confusion in voters' minds. They trust Republicans even less than Democrats, but seem prepared to vote them back in anyway. Weird. "Throw the rascals out" irrationally trumps "better the devil you know".

On the face of it, I think you are in for a very bad two years of Tea Party screeching. At any rate having to use the veto every week may cure Obama of his bipartisan dreams, and force him to bend his considerable talents to the political destruction, not taming, of his irreconcilable enemies.

That's a lower bound on the error bar, assuming that they didn't have to do any renorming at all, assuming their response rate was 100%, and so on, and so forth. The likelihood of which I'd put somewhere between little and none.

Realistically, the error bar on a poll like this is probably more like 5-6%.